The goal of this project is to map and identify genes for syndromic and nonsyndromic forms of herditary deafness. Linkage analyses are being conducted using large pedigrees segregating non-syndromic or syndromic forms of deafness. If linkage to a known syndromic, DFNA (dominant) and DFNB (recessive) locus in large families is excluded, we initiate a genome-wide screen. During the past year this strategy has allowed us to map new deafness loci including DFNB63 and DFNB72, and to identify DFNB24 (RDX). The chromosomal map locations of novel deafness loci are refined prior to initiating positional cloning strategies to identify the genes responsible for the hearing loss. Additional families with dominant and recessive modes of inheritance with profound congenital or progressive hearing loss are being ascertained with the goal of mapping and cloning additional novel genes that are necessary for hearing and/or maintenace of the auditory system. We are also ascertaining families, mapping loci and identifying genes for Usher syndrome. The defining clinical features of Usher syndrome are hearing loss and progressive retinopathy. We are continuing to study the functions in the inner ear of cadherin 23 (USH1D) and protocadherin 15 (USH1F) and have demonstrated as a collaboration with Guy Richardson's group that a novel isoform of protocadherin 15 is a component of the hair cell tip-link transduction complex (Ahmed et al. 2006).